Inductive control circuits



April 27, 1937. A. H. BROWN, JR 2,078,232

INDUCTIVE CONTROL CIRCUITS Filed July 19, 1935 2 Sheets-Sheet 1 INVENTOR. R Z (am/Mew A. Bra rm, J)".

ATTORNEY.

April 27, 1937. A. H. BROWN JR INDUCTIVE CONTROL CIRCUITS Filed July 19, 1935 2 Sheets-Sheet 2 INVENTOR. /7ZXd nder HBrvn n 11/".

ATTORNEY.

Patented Apr. 27, 1937 UNITED STATES INDUCTIV E CONTROL CIRCUITS Alexander H. Brown, In, New York, N. Y., assignor, by mesne assignments, to Transit Research Corporation, New York, N. Y., a corporation of New York Application July 19, 1935, Serial No. 32,159

29 Claims.

This invention relates to control means for di rect current and has for its object to provide a control of inductive type whereby direct current at one potential may be transformed to direct 5 current at another potential without substantial loss, the delivered potential being either higher or lower than that of the source of supply.

Another object is to provide a direct current control which will give a vastly greater degree of flexibility of the voltage ratio control than is attainable, for example, in a motor generator set, and which is capable of stepping the voltage up or down throughout this range with smoothness of delivered power and at the same time without the losses which occur, for instance, with rheostatic control.

More particularly it is an object to provide conductor at high potential, a conductor at low potential and a relatively large inductance in the low potential conductor, to intermittently connect and disconnect the conductor at high potential with the inductive low potential conductor circuit, and to employ the inductance as a means for impelling a current flow by virtue of the induced voltage upon interruption (or establishment, as the case may be) of the connection between the high and low potential conductors.

The inductance is above referred to as being in series with the low potential circuit. Actually the inductance may be incorporated in a low potential unit of apparatus itself in some cases, as where the unit is a motor or a generator, for instance, but the effect is essentially the same as where an inductor is placed in Series with the low potential unit of apparatus. I thus provide a cycle involving the steps of high potential application to the low potential circuit, disconnection of the high potential from the low potential circuit with simultaneous short circuiting of the 40 low potential circuit, current flow through the low potential circuit maintained by the inductance, and re-connection of the inductive low potential circuit with the high potential circuit with simultaneous interruption of the short circuit aforementioned. This cycle entails rapid making and breaking of circuits usually carrying sunicient power to cause arcing at contact points so serious as to be destructive. It is, therefore, another object of this invention to provide means 50 for preventing all detrimental arcing at all points of make and break and in fact to remove the tendency to are as will be hereinafter more fully explained. The fulfill sent of this object has led to the provision of arc prevent ive means in the form of a circuit and contactor arrangement and also in the form of conductor construction having adaptability both individually and jointly in any direct current use where arcing is to be avoided and hence is not limited to inductive con- Cir 50 trol apparatus. A specific object is to teach the construction of a conductor for distributed capacity over any given linear length which will give an electrical effect analogous to an infinite number of condensers along that length.

A further object of the invention is to provide means for altering the stages or steps of the above mentioned cycle as to time of duration so that the transmission of power in either direction may be accomplished at an increasing, constant, or a decreasing rate.

The invention as described to this point contemplates a circuit adapted to deliver current either to or from a relatively high potential. Another object is to teach the simplification of the circuit for installations in which the transformation is always from a higher to a lower potential or vice versa.

The invention in its entirety is adaptable, for example, to the control of electric railway cars where the starting and norm-a1 running is accomplished by the application of power from a transmission line to the motors, and where it is also desirable to re-convert the energy of decelerating from kinetic to electric energy and for feeding this reconverted electric energy back into the line. The control circuit may, by simplification as above referred to, be arranged so that the regenerative feature is omitted, and it may be arranged also so that the regenerative feature alone is used. Other examples of suitable installations of my invention in one form or another are as follows:

Elevator control;

Steel mill motor control;

Welding power supply;

Electroplating power source;

Battery charger;

Trolley bus control;

Diesel generator type stream line train accelerating and braking control;

Subway and elevated accelerating and braking control;

As a means for raising a low generated D. C.

voltage to a high D. C. voltage for long distance transmission;

High voltage D. C. supply for broadcasting stations;

Electric locomotive control;

In general, wherever it is advisable to transform D. C. power at one potential to D. C. power at another potential dependably and without serious energy loss.

Other objects and advantages will become more fully apparent as reference is had to the accompanying drawings wherein my invention is diagrammatically illustrated and in which Figure 1 is a diagrammatic illustration of a circuit in accord with this invention,

Figure 2 is a, graph of a power curve which may be obtained by my improved circuits,

Figure 3 is a modified form of the circuit of Figure 1,

Figure 4 is a composite of the circuits of Figures 1 and 3, and

Figure 5 is a circuit making and interrupting device designed for rapid operation.

The composite circuit is illustrated in Figure 4. When the several contactors are thrown to a position for transforming the current from a higher to a lower potential the circuit is then as illustrated in Figure 1. When the several contactors are thrown to a position for transforming the current from a lower to a higher potential the circuit is then as illustrated in Figure 3.

With reference first to Figure 1, a conductor I from a suitable source of power has a terminal 2 for a contactor S whereby it may be connected and disconnected to a relatively large inductance 3 and a load 4. As will hereinafter more fully appear, the contactor S may be of any desired form but is preferably capable of rapid, intermittent opening and closing in a way more or less analogous to the action of a commutator. The load 4 may be any means for using electrical energy, as hereinbefore referred to, and the inductance may, in some cases, as in motors for example, be inherent in the load. In other cases the load 4 may be positioned between the inductance 3 and the contactor S.

Leading from a, point 5 between the contactor S and the inductance-load 3, 4 is a conductor grounded at 6 and having a rectifier I therein through which no current can flow in the direction of the ground but through which current may flow from the ground. As will hereinafter appear, this rectifier I may be replaced by a (timed) switch or contactor if desired. The rectifier is preferred because it is impossible to ground the line I at 6 by accident. It is recognized, however, that it takes a potential across the rectifier to obtain a current flow therethrough and hence that a contactor may, in some cases, prove to be preferable.

The load 4 is grounded as at 8 or a return line to the source of power supply is otherwise provided. With the circuit thus far described, when S is closed current flows through the inductance 3 and through the load 4. Upon breaking the circuit by opening the contactor S, the induced voltage in the inductance 3 tends to maintain a current flow through the load in the established direction. By virtue of the grounded rectifier I, the tendency of the induced voltage to maintain a current flow for an appreciable time is accommodated, and hence, the inductor circuit is from the inductance 3 through the load 4 to its ground 8, thence upwardly through the ground 6, through the rectifier 'I and to the inductance 3. Upon reclosing S after a short interval the current fiow continues in the same direction but, since the current from the source I comes in at a higher potential, the current flow through the rectifier 1 is interrupted. If the period or interval during which S is open is sufficiently short a continuous current flow to the load will result.

When the contactor S is first closed the current flow to the load will not be instantaneous because of the inertia of the inductance. It will build up gradually, and hence, if S is opened before the complete build up, the increase in current flow to the load can be terminated, with proper pparatus, with the current at any predetermined value. The current value may then be allowed to drop to any desired value, the exact value to which it drops depending upon the length of time S remains open, and hence the current, when S. is closed again, may be greater than at the time S was first closed. This is graphically illustrated in Figure 2, wherein the ordinate represents current through the inductance and the abscissa represents time. After closing the contactor S, the current flowing through the inductance rises until it attains a value a, whereupon S opens and stays open until the current falls to a value b. This completes one cycle, which is composed of two stages or steps, the first being shown on the graph by the line from the origin to the point "a which represents rising or increasing current, the second being shown on the graph by the line from the point a to the point 12" which represents falling or decreasing current. The point b represents the end of the first cycle. The contactor S is then closed whereupon the current builds up to a new value a, and so on. The cycle is indicated by At and this is the period of the cycle. Variation of this period varies the frequency. Variation of vthe relative time of duration of each stage or step of the cycle varies the rate of power delivery. As illustrated in Figure 2, at the top of the graph, the mean rate of current delivery may be made constant by con' trolling the time intervals of the two stages. In other words, if the first stage of each cycle is shortened and the second stage is lengthened, the rise of current from the beginning of the cycle to the peak will be lessened, and the drop from the peak to the end of the cycle will be increased, and the drop can be made equal to the rise. Each cycle, as shown at the top of the graph, will begin with the same current as the previous one, and the mean current will be constant. By making the duration of flow through the inductive circuit when S is open relatively longer with respect to the duration of flow when S is closed, current and hence power may be delivered at a decreasing mean rate, as would be shown, for instance, by the reverse of the rising part of the graph. By gradually varying the relative lengths of the two portions of the cycle, the rate at which current and power are being delivered can be made to increase or decrease.

The control as described to this point would ordinarily entail destructive arcing at the contactor. In order to reduce this arcing as far as possible and at least to the point where it is not detrimental, a conductor is led from the line at the point 5 to a ground 8 and between this ground and the point 5 is interposed a condenser 9, an inductor II] and a resistance II. A contactor s bridges the inductor I0 and the resistance II. Upon closing the contactor S, the contactor s is kept open so that current flow to the condenser must necessarily traverse the inductor I0 and the resistance II. The effect would be the same if the inductor I0 and the resistance II were actually placed between the ground 8 and the condenser 9. Current from the source I can not, therefore, rush into the condenser 9 instantaneously, and hence an excessive current can not fiow instantaneously through the contactor S. This retarding action, therefore, permits a closing of S without substantial arcing even though the source I be at a high potential. After current has stopped flowing into the condenser 9, the potential across the switch 8 is balanced, since the resistance II prevents oscillations. and

this switch 5 may therefore be closedwithout arcing.

Upon opening the contactor S with 3 closed, the stored energy of the condenser 9 is practically instantaneously available to oppose a drop in potential across S during opening thereof. The potential of the point 5, just as S opens. will be substantially the potential of the source I but will, of course, fall rather rapidly. The speed of opening of S is at a rate such that the increasing gap furnishes an increasing resistance to arcover which, measured in volts, increases faster than the potential difference increases across the contactor S. This materially reduces and in some cases practically eliminates detrimental arcing during the opening of the switch S.

There may still be a slight arcing due to oscillations of current and variations of potential in the supply line, particularly where other loads are applied between the source of power generation and the circuit under consideration. I therefore interpose an inductance I2 in the power line I and between this inductance and the terminal 2 is a condenser I3 grounded at I4, this condenser being as close as possible to the terminal 2.

Due to the fact that the condensers 9 and I3 may, because of practical exigencies of installation, be at a considerable distance from the terminals of the contactor S it may prove highly desirable to have additional condenser effect and I therefore provide a spaced, grounded, conductive sheathing I5 for the conductors over a substantial portion of their length and preferably over .the entire conductor length between the condensers 9 and I3 and the contactor S in order to obtain distributed capacity over the entire length thereof. This conductor construction is more fully described and claimed in my co-pending application, Serial Number 32,485 filed July 22, 1935 and hence is only diagrammatically illustrated herein.

In order to alter the circuit of Figure 1 into that of Figure 3, it will be seen in Figure 4 that the power line I is interrupted at It and the contactor at that point is thrown to the terminal II in order to ground the contactor S at IS; the condenser 53 is disconnected at I9 from the ground 8 and connected by the terminal 29 into the power line I at a conveni nt point 2!; the rectifier i disconnected at 22 from line S5 and connected at 23 with the power line I; and the rectifier l is disconnected at 24 from the ground 6 and connected at the terminal 25 into the circuit with the inductance 3 and load 4 at some convenient point 26; if the low potential apparatus 4 is to constitute a. source of power it will usually be in the form of a motor which can be converted into a generator. Where it is a motor and operating under the power supplied by the line i, as indicated in Figures 3 and 4, the armature A may be in series with the field F and grounded at 21. In order to convert this motor into a generator the field F is reversed so that the armature A is in series with the field F which is grounded at 28 and the ground connection at 2? is interrupted. The circuit is then arranged to transform current from the low potential apparatus t to the high potential line I. In the case of electric railway cars, for instance, this change-over would be made manually at the time of converting the motors into generators whereupon the kinetic energy of the travelling car can be converted into electrical energy and fed back into the power line.

A number of ways of converting a series of motor circuits into generator circuits suitable for connection to the circuits herein described are well known in the art and need not be illus trated herein. While most of those ways would be suitable with the circuits illustrated, the preferred form is the one shown.

With reference now to Figure 3. during the first part of braking, the contactor S is closed continuously on the terminal 2 because the motors are then building up current and this ground at I8 permits this build-up to a value capable of producing the desired braking rate. The contactor s is also closed and remains closed subsequent to the opening of S. As the contactor S opens, the current which. was flowing through the contactor S begins to flow through 5, s, 29, 9, 2G and into the power line at EI. The potential at 5 rises gradually from the ground potential of I8 as this current charges the condenser 9. opened, the potential at 5 is substantially at ground, and S starts opening without appreciable voltage drop across the gap, so that no arcing of consequence occurs at that time. As

the gap increases, the potential at 5 rises at a rate where I is the current through the condenser 9 2,,

the rectifier T, the potential at 5 ceases rising and current stops flowing between 25, 5, s and 29. The contactor s then opens without arcing and the current through 3 then flows through the circuit 25, 25, I and into the line at 23. This flow of current which is furnished by the inductance 3 and the motor-generators drops rather rapidly. After it has dropped to a certain value, S closes and the terminal 26 assumes ground potential. The current through 3 thereupon flows at an increasing rate through the circuit 26, 5, S, 2, i! into 88. coincidentally current flows from El through the circuit 28, 9, 29, I0, ll, 5, S, 2, I"! and into I8. This current fiow is prevented from reaching harmful magnitude at the instant S closes by the inductance I0 and is prevented from being of an oscillatory nature by the resistance II. The potential at 29 decreases at a rate where I is the current through I0 and C is the capacity of the condenser 9. As soon as the potential at 29 has decreased to the potential at 5, current ceases to flow in this circuit I5, H and. the switch 3 is closed.

The proportions between the inductance IE3 and the resistance II are such that current ceases to flow when the potential at 23 has dropped substantially to the potential at 5, at which time the contactor s can be closed without a sudden current surge from the condenser 9 which would otherwise damage this contactor. The rectifier may, in this case also be replaced by a timed contactor.

As the contactor S remains closed the current through the inductance 3 continues to increase to a certain value; then 3 opens etc, as EtfOlxr described.

Briefly, this cycle is as follows: S closes first, the current flow through it being damped by At the beginning when S is first the inductor l0 and current begins flowing through 3. When the points 28 and 5 have reached a balanced potential, 8 is closed. After a current build up in the inductance 3, then S opens. A current flow takes place into the condenser 9 and into the power line at 2|. As soon as the potential in the line 26, 5, s, 9, 20, 2| has risen to a value equal to the potential across the rectifier, current begins to flow through the rectifier, current no longer flows through the condenser 9, the potential across 8 is therefore balanced and s is then opened. Current flows into the power line under impulsion by the inductance 3 in an amount and at a rate depending upon the value to which the current was allowed to build up in 3 before opening the contactor S and according to the time when 3 is open before S again closes. By varying these factors the rate of regeneration and hence the rate of braking may be altered. As an example, the stepped curve of Figure 1 may likewise be a braking curve and these time intervals may be altered by the same mechanism and in the same manner as is required for operation of the circuit illustrated in Figure 1 as will now be described.

The various times of opening and closing of the contactors S and s require a device which will function with the desired rapidity and which will give the desired sequence and intervals of operation. A number of devices and circuits can be devised which will give the cycle desired. In Figure 5, such a device is illustrated. A small motor 30 has a shaft 3| journalled in a support 32 and fixedly attached to this shaft is a cylinder 33 made of a non-conductive material. Carried by the surface of this cylinder are two bands 34 and 35 of conductive material each having a plurality of serrations 36 and 31 respectively. A bracket 38 is journalled on the shaft 3| at each end of the cylinder 33, the shaft being rotatable in the journals and the journals being longitudinally slidable on the shaft. This bracket 38 carries two brushes in insulated relation therewith which are the contactors S and s aforementioned. The other two brushes 39 and 48 are each connected to the point 5. These brushes 39 and 40 are in constant contact with the bands 34 and 35 respectively. The brushes S and s, however, are adapted for intermittent contact with the serrations 36 and 31. By moving the bracket 38 longitudinally, by means of the handle 4|, the relative period of connection and disconnection of the brushes 5 and s with the serrations 36 and 31 can be altered and contact with the bands 34, 35 can be established. Rotation of the bracket 38 with or against the direction of rotation of the cylinder is an example oi how to vary the period of the cycle. Any other means of changing the rotational speed of the drum relative to the bracket, such as changing the speed of the drum, will accomplish the same result.

It will be noted that the serrations 36 are not alined with the serrations 31 but, with rotation of the cylinder in the direction as indicated by the arrow, lag therebehind. This means that the switch .9 will always be closed when S opens and will remain closed for a time after S opens. S always precedes s in closing.

What I claim is:

1. In combination, a conductor at high potential, a conductor at low potential, an inductance associated with the low potential conductor, means for connecting and disconnecting said high potential conductor from said inductance and low potential conductor, and a second means operative upon disconnection of said conductors for establishing a separately complete circuit including said inductance and low potential conductor whereby current continues to flow through said inductance in its established direction, said second means being operative to interrupt said separate circuit upon reconnection of said conductors.

2. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, means for intermittently connecting and disconnecting said high potential conductor to and from said inductance and said low potential conductor, and means for breaking said circuit upon connection of said high potential conductor to said inductance and said low potential conductor, said last named means operating to re-establish said circuit during the period of disconnection of said high potential conductor.

3. The combination of a direct current circuit including an inductance and a low potential conductor, a high potential conductor, means for intermittently connecting and disconnecting said high potential conductor to and from said inductance and said low potential conductor, and a grounded rectifier having one terminal connected between said high potential conductor and the inductive low potential conductor opposing the flow of current therethrough in the direction toward ground.

4. The combination 01' a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, and means for maintaining a substantially balanced potential across said contactor during opening thereof whereby the possibility of arcover is materially reduced.

5. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, means for storing an amount of electrical energy between said contactor and said inductance at the potential of said high potential conductor, the potential due to the storing of said energy belng practically instantaneously available upon the opening of said contactor to oppose a detrimental potential drop across said contactor during opening thereof, and means for utilizing said stored energy to do useful work subsequent to the opening of said contactor.

6. The combination as set forth in claim 5 characterized in that the means for utilizing the stored energy is connected to assist in maintaining a current flow through said inductance and said low potential conductor following the opening of said contactor.

7. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittent- 1y connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, and means for storing an amount of electrical energy between said contactor and said inductance at the potential of said high potential conductor, the potential due to the storing of said energy being practically instantaneously available upon the opening of said contactor to oppose a detrimental potential drop across said contactor during opening thereof.

8. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, means for gradually storing an amount of electrical energy between said contactor and said inductance until the potential of said high potential conductor is reached, and means for rendering said energy practically instantaneously available upon the opening of said contactor whereby the potential across said contactor is maintained at a value which materially reduces the possibility of arcover during the opening thereof.

9. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, means for storing an amount of electrical energy between said contactor and said inductance for practically instantaneous availability upon opening of said contactor, and means for preventing oscillations of potential at said means for storing whereby arcover during contactor opening is materially reduced.

10. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, means for maintaining the line between said contactor and said inductance substantially at the potential of said high potential conductor during the opening of said contactor and means for reducing variations of potential in said high potential conductor during the opening of said contactor whereby destructive arcing is precluded.

11. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, means for maintaining the line between said contactor and said inductance substantially at the potential of said high potential conductor during the opening of said contactor, means for damping current oscillations in said line, and means for damping current oscillations in said high potential conductor during the opening of said contactor whereby the possibility of destructive arcing is reduced.

12. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, and means for substantially precluding arcing during the opening of said contactor comprising means for storing electrical energy between said contactor and said inductance at the potential of said high potential conductor and means for opening said contactor at a rate such that the increasing gap thereof furnishes an increasing resistance to arcover, which, measured in volts, increases faster than the potential difference increases across said gap.

13. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, and means for substantially precluding arcing during opening of said contactor comprising an electrical line connected at one end to the electrical connection between said contactor and said inductance and having a condenser therein, an inductor in said line between said contactor and said condenser, a shunt icy-passing said inductor and having a switch means therein for directly connecting said condenser and said contactor upon closing thereof, the switch means in said shunt being open during the charging of said condenser and closed after the potential across the terminals of said inductor is balanced, the means for opening said contactor functioning subsequent to the closing of the switch means in said shunt.

14. The combination of a circuit comprising an inductance and a low potential conductor, a high potential conductor, a contactor for intermittently connecting and disconnecting said high potential conductor to and from said inductance and low potential conductor, the current around said circuit being interrupted upon the closing of said contactor, means for reestablishing said current and for maintaining said current during the period when said contactor is open, and means for substantially precluding arcing during opening of said contactor comprising an electrical line connected at one end to the electrical connection between said contactor and said inductance and grounded at its other end, a condenser in said line and an inductor and a resistor in said line between said condenser and said contactor, a

shunt across said inductor and said resistor having a switch therein, timed means for maintaining said switch open during the charging of said condenser and for closing said switch after the potential across the terminals of said inductor and said resistor has become balanced, and timed means for opening said contactor after the closing of said switch.

15. The combination as set forth in claim 12 together with means for reducing variations of potential at said high potential conductor during the opening of said contactor.

16. An electrical circuit including a source of electrical energy, an inductance and a contactor between said inductance and said source, means for intermittently opening and closing said cons tactor, and means between said contactor and said inductance for storing electrical energy in sufficient quantity to maintain the side of said contactor toward said inductance at substantially the same potential as that of the side of said contactor toward said source of energy during the time of opening of said contactor whereby detrimental arcing at said contactor is preeluded.

17. An electrical circuit including a source of electrical energy, an inductance, and a contactor between said source and said inductance adapted to intermittently open and close the circuit, means for storing electrical energy between said contactor and said inductance at the potential of said source, and means for opening said contactor at a rate such that the increasing gap furnishes an increasing resistance to arcover which, measured in volts, increases faster than the potential difference across the contactor.

18. The combination as set forth in claim 16 wherein the means for storing electrical energy comprises a conductor, a condenser connected to said conductor, a second inductance in said conductor and a switch means which when closed bridges said second inductance, and means for closing said switch means.

19. The combination as set forth in claim 16 wherein the means for storing electrical energy comprises a conductor, a condenser connected to said conductor, a second inductance and a resistance in series in said conductor, and a switch means which when closed bridges said inductance and said resistance, and means for closing said switch means.

20. The combination as set forth in claim 16 wherein the means for storing electrical energy comprises a conductor, a condenser connected to said conductor, a second inductance and a resistance in series in said conductor, and a switch means which when closed bridges said inductance and said resistance, and means for closing said switch means, the means for opening said contactor being timed to function only after said switch means has closed.

21. The combination as set forth in claim 16 wherein the means for storing electrical energy comprises a conductor, a condenser connected to said conductor, an inductor and a resistance in series in said conductor, and a switch across said inductor and resistance, timed means for closing said switch when the potential across the terminals thereof becomes balanced, and timed means for opening said contactor subsequent to the closing of said switch, the stored energy being available to said inductance for assistance in maintaining a current flow therethrough following the opening of said contactor.

22. The combination of a conductor at high potential, a conductor at relatively low potential having an inductance associated therewith, means for supplying metered amounts of power to said inductance and said low potential conductor comprising an intermittently opening and closing contactor, said inductance being adapted to maintain a current flow through said low potential conductor in the established direction when said contactor is open, and means for regenerating current into said high potential conductor comprising means for destroying the current flow through said inductance and said low potential conductor, means for completing a circuit including said inductance and said low potential conductor and constituting a source of power whereby current begins to build up in said inductance in opposite direction to the current aforementioned, and means for interrupting said last named circuit and for establishing a current from said inductance and low potential conductor to said high potential conductor whereby current is fed into said high potential conductor, and means for interrupting said connection with said high potential conductor and for re-establishing the circuit comprising said inductance and low potential conductor whereby current is again allowed to build up in said inductance.

23. The combination of a conductor at high potential, a conductor at relatively lower potential having an inductance associated therewith, means for completing a circuit comprising the low potential conductor and said inductance and in which current flows toward said high potential conductor, timed means for interrupting said circuit and for connecting said inductance and low potential conductor to said high potential current whereby current is fed into said high potential conductor, and timed means for re-establishing said circuit and for interrupting the flow of current into said high potential conductor after a predetermined interval whereby current again begins to build up in said circuit.

24. The combination of a conductor at high potential, a second conductor at relatively lower potential having an inductance and a load associated therewith, said second conductor being grounded, a make and break device for connecting and disconnecting said conductors, and a. second ground for said second conductor on the opposite side of said inductance and load from the first ground, said second ground being operative only during periods of disconnection of said conductors whereby current continues to flow around said second conductor to said load during such periods of disconnection.

25. The combination of a source of electrical power at high potential, a conductor having a load and an inductance associated therewith, said conductor being grounded on the side of the load away from said source of power, timed means for connecting said source to said conductor, said timed means interrupting the connection after a predetermined period of time during which the current flow in said conductor to said load has built up to a substantial value, means completing a circuit for said conductor, said inductance and said load upon interruption of said connection whereby current continues to flow to said load at least partially impelled by said inductance, said timed means again establishing said connection after a predetermined time during which the current in said conductor to said load has fallen a substantial amount, and means for controlling said periods of time relatively whereby current may be supplied to said load at an increasing, a decreasing or a constant rate.

26. The combination of a source of electrical power at high potential, a conductor having a load and an inductance associated therewith, said conductor being grounded on the side of the load away from said source of power, timed means for connecting said source to said conductor, said timed means interrupting the connection after a predetermined period of time during which the current flow in said conductor to said load has built up to a substantial value, means completing a circuit for said conductor, said inductance and said load upon interruption of said connection whereby current continues to flow to said load at least partially impelled by said inductance, said timed means again establishing said connection after a predetermined time during which the current in said conductor to said load has fallen a substantial amount, and means for varying the length of each of said periods of time.

27. The combination of a source of electrical power at high potential, a conductor having a load and an inductance associated therewith, said conductor being grounded on the side of the load away from said source of power, timed means for connecting said source to said conductor, said timed means interrupting the connection after a predetermined period of time during which the current flow in said conductor to said load has built up to a substantial value, means completing a circuit for said conductor, said inductance and said load upon interruption of said connection whereby current continues to flow to said load at least partially impelled by said inductance, said timed means again establishing said connection after a predetermined time during which the current in said conductor to said load has fallen a substantial amount, and means for varying the sum of said periods of time.

28. The combination of a source of electrical power at high potential, a conductor having a load and an inductance associated therewith, said conductor being grounded on the side of the load away from said source of power, timed means for connecting said source to said conductor, said timed means interrupting the connection after a predetermined period of time during which the current flow in said conductor to said load has built up to a substantial value, means completing a circuit for said conductor, said inductance and said load upon interruption of said connection whereby current continues to flow to said load at least partially impelled by said inductance, said timed means again establishing said connection after a predetermined time during which the current in said conductor to said load has fallen a substantial amount, and means for varying both the relative lengths and the sum of said periods of time.

29. The combination of a source of electrical power at high potential, a conductor having a load and an inductance associated therewith, said conductor being grounded on the side of the load away from said source of power, timed means for connecting said source to said conductor, said timed means interrupting the connection after a predetermined period of time during which the current flow in said conductor to said load has built up to a substantial value, means completing a circuit for said conductor, said inductance and said load upon interruption of said connection whereby current continues to flow to said load at least partially impelled by said inductance, said timed means again establishing said connection after a predetermined time during which the current in said conductor to said load has fallen a substantial amount, and means for maintaining a substantially balanced potential across the terminals of said contactor during the instants of interruption of the current flows.

ALEXANDER H. BROWN, JR. 

